Now in its 15th year, the Best Illusion of the Year contest has named their 2019 winner. Top prize went to Frank Force, an Austin-based game developer who created this “Dual Axis Illusion:”
I especially appreciate that Force shows you the trick for how to change your perception of the direction of rotation.
If you want to see more brain-breakers from the contest, click here.
https://www.core77.com/posts/91971/Best-Illusion-of-the-Year-You-Cant-Tell-if-This-Shape-is-Rotating-on-the-Horizontal-or-Vertical-Axis